Reverse Recovery Current Research Articles

Single-Chip Boost Converter Using Monolithically Integrated AlGaN/GaN Lateral Field-Effect Rectifier and Normally Off HEMT

We demonstrate a single-chip switch-mode boost converter that features a monolithically integrated lateral field-effect rectifier (L-FER) and a normally off transistor switch. The circuit was fabricated on a standard AlGaN/GaN HEMT epitaxial wafer grown with GaN-on-Si technology. The fabricated rectifier with a drift length of 15 mum exhibits a breakdown voltage of 470 V, a turn-on voltage of 0.58 V, and a specific on-resistance of 2.04 mOmegaldrcm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The L-FER exhibits no reverse recovery current associated with the turn-off transient because of its unipolar nature. A prototype of GaN-based boost converter that includes monolithically integrated rectifiers and transistors is demonstrated using conventional GaN-on-Si wafers for the first time to prove the feasibility of the GaN-based power IC technology.

An Alternative Energy Recovery Clamp Circuit for Full-Bridge PWM Converters With Wide Ranges of Input Voltage

A full-bridge DC-DC converter employing a diode rectifier in the output experiences a severe voltage overshoot and oscillation problem across the diode rectifier caused by interaction between junction capacitance of the rectifier diode and leakage inductance of the transformer. The pronounced reverse-recovery current of high-power diodes significantly contributes to these issues by increasing power lossand voltage overshoot. Conventional energy recovery clamping circuits suffer from high voltage overshoot if the converter input voltage is wide. In this paper, a novel energy recovery clamp circuit is proposed to overcome this problem. The proposed circuit requires neither active switches nor lossy components. Therefore, the proposed circuit is very promising in high-voltage and high-power applications. Performance of the proposed circuit is verified both theoretically and experimentally with a 70-kW DC-DC converter.

Transient reverse current phenomenon in a p-n heterojunction comprised of poly(3,4-ethylene-dioxythiophene):poly(styrene-sulfonate) and ZnO nanowall

We report the characteristics of a p-n heterojunction diode comprised of a poly(3,4-ethylene-dioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) as the hole-conducting p-type polymer and n-type ZnO nanowall networks. ZnO nanowall networks were synthesized on a GaN/sapphire substrate without metal catalyst using hot-wall type metal organic chemical vapor deposition. The p-n heterojunction diodes of PEDOT:PSS/ZnO nanowall exhibited a space charge limited current phenomena at forward bias and a transient reverse current recovery when a sudden reverse bias was applied from the forward bias condition. The minority carrier lifetime was estimated to be ∼2.5 μs.

An IGBT Gate Driver for Feed-Forward Control of Turn-on Losses and Reverse Recovery Current

This paper addresses the problem of turn on performances of an insulated gate bipolar transistor (IGBT) that works in hard switching conditions. The IGBT turn on dynamics with an inductive load is described, and corresponding IGBT turn on losses and reverse recovery current of the associated freewheeling diode are analysed. A new IGBT gate driver based on feed-forward control of the gate emitter voltage is presented in the paper. In contrast to the widely used conventional gate drivers, which have no capability for switching dynamics optimisation, the proposed gate driver provides robust and simple control and optimization of the reverse recovery current and turn on losses. The collector current slope and reverse recovery current are controlled by means of the gate emitter voltage control in feed-forward manner. In addition the collector emitter voltage slope is controlled during the voltage falling phase by means of inherent increase of the gate current. Therefore, the collector emitter voltage tail and the total turn on losses are significantly reduced. The proposed gate driver was experimentally verified and compared to a conventional gate driver, and the results are presented and discussed in the paper.

The Current Sharing Optimization of Paralleled IGBTs in a Power Module Tile Using a PSpice Frequency Dependent Impedance Model

A full circuit model of an insulated gate bipolar transistor (IGBT) power module tile is obtained using electro-magnetic analysis. A skin depth analysis on the copper and bonding wire interconnects shows that the commonly used low frequency RLC models are not adequate for power modules and reveals the necessity for a frequency dependent impedance. A method is adapted for the design of an f-dependent module tile design circuit for the first time. It is found that the importance of skin depth becomes vital especially for lower voltage ratings and faster edge rate devices as the Fourier transform becomes shifted towards higher frequencies. Analysis of the current sharing capability of the IGBTs as a function of the tile layout showed that an asymmetrical tile yields a faster response from the nearer IGBTs during inductive turn-off and an unbalanced sharing of the reverse recovery current during turn-on. A symmetric tile layout is developed. It is found that the faster current fall-time during turn-off is compensated by higher current tail oscillations thereby bringing no major improvement to the turn-off energy. During turn-on however, the reverse recovery and IGBT turn-on energy dissipation are equally distributed between the IGBTs. Simulating device imbalances also shows that threshold voltage variations have a significant effect on the current and energy sharing at turn-on whereas injection efficiency imbalances have a large influence on turn-off characteristics. The effect of device imbalances is found to decrease for a highly symmetric tile design. It is also shown that equally higher IGBT temperatures tend to improve current sharing so that IGBT module design emphasis should be placed rather on minimizing any differences in the IGBT junction temperatures. The model developed allows PSpice simulation of characteristics previously obtained only through measurements. The impact of the layout design on issues such as cross-talk, mutual inductance and ground bounce may be quickly and accurately assessed for an optimal current sharing capability.

Bridgeless Boost Rectifier With Low Conduction Losses and Reduced Diode Reverse-Recovery Problems

A bridgeless boost rectifier with low conduction losses and reduced diode reverse-recovery problems is proposed for power-factor correction. The proposed boost rectifier can reduce the conduction losses and alleviate the diode reverse-recovery problems by using a coupled inductor and two additional diodes. Zero-current turn-off of the output diodes is achieved, and the reverse-recovery currents of the additional diodes are slowed down to reduce the diode reverse-recovery losses. All inductive components are realized on a single magnetic core by utilizing the leakage inductance of the coupled inductor. Furthermore, for the use of this topology in the practical design, the linear peak current mode control is employed for the proposed boost rectifier. A detailed analysis and a control strategy are presented. Experimental results for a 300-W prototype are also discussed to show the performance of the proposed boost rectifier

High-Efficiency DC-DC Converter With High Voltage Gain and Reduced Switch Stress

In this paper, a high-efficiency dc-dc converter with high voltage gain and reduced switch stress is proposed. Generally speaking, the utilization of a coupled inductor is useful for raising the step-up ratio of the conventional boost converter. However, the switch surge voltage may be caused by the leakage inductor so that it will result in the requirement of high-voltage-rated devices. In the proposed topology, a three-winding coupled inductor is used for providing a high voltage gain without extreme switch duty-cycle and enhancing the utility rate of magnetic core. Moreover, the energy in the leakage inductor is released directly to the output terminal for avoiding the phenomenon of circulating current and the production of switch surge voltage. In addition, the delay time formed with the cross of primary and secondary currents of the coupled inductor is manipulated to alleviate the reverse-recovery current of the output diode. It can achieve the aim of high-efficiency power conversion. Furthermore, the closed-loop control methodology is utilized in the proposed scheme to overcome the voltage drift problem of the power source under the variation of loads. Some experimental results via an example of a proton exchange membrane fuel cell power source with 250-W nominal rating are given to demonstrate the effectiveness of the proposed power conversion strategy

High-efficiency single-stage bidirectional converter with multi-input power sources

A multiple-input, single-stage bidirectional converter is proposed. It takes a three-winding coupled inductor as the main component of energy transmission, and utilises only two switches to accomplish the multi-input mechanism. Depending on the switching conditions, the circuit can be operated at discharge, charge and alone states. The winding voltage in the high-voltage side of the coupled inductor is manipulated to further increase the corresponding voltage gain, a strategy that is superior to one in the conventional coupled-inductor. This topology is useful for low-power applications. In addition, all switches and diodes have favourable voltage-clamping effects so that the voltage spikes caused by the leakage-inductor energy can be alleviated effectively, and reverse-recovery currents within diodes can be reduced, because the leakage inductor has limited capability to handle quick current changes. There is also a low-voltage-type charge circuit with no increase in additional circuit elements. This helps -to avoid power losses that arise from multistage conversions in traditional auxiliary power systems. This strategy also utilises the synchronous rectification technique to further decrease conduction losses. Numerical simulations and experimental results via examples of a proton exchange membrane fuel cell power source and a traditional battery module are given to demonstrate the effectiveness of the proposed power conversion strategy.

Influence of parasitic inductances on transient current sharing in parallel connected synchronous rectifiers and Schottky-barrier diodes

The transient current sharing in parallel connected Schottky-barrier diodes and MOSFET synchronous rectifiers is analysed. It is shown that, because of parasitic inductances the desired reduction of dead-time conducting losses and reverse-recovery peak current is limited, when discrete devices are used. The total amount of conducting losses in the free-wheeling circuit can increase. A reduction of switching losses in half-bridge configurations is possible because of secondary effects.

High-performance light emitting diode backlight driving system for large-screen liquid crystal display

A high-performance light emitting diode backlight driving system is proposed for large-screen liquid crystal display. The proposed system consists of a boost converter for power factor correction (PFC) and an active-clamp converter for dc–dc power conversion. With coupled inductors and simple passive components, the proposed PFC circuit minimises the switching losses by reducing the reverse-recovery current. The active-clamp converter operates under zero-voltage switching for the power switches and its output rectifier is composed of a current doubler and a synchronous rectifier for reducing conduction loss. The proposed backlight driving system is analysed and its design consideration is discussed in detail. Experimental results for a 300 W (3.3 V/90 A) prototype at a constant switching frequency of 100 kHz are presented to verify the analysis and the performance of the proposed system.

High-Temperature (up to 800 K) Operation of 6-kV 4H-SiC Junction Diodes

Steady-state and transient characteristics of packaged 6-kV 4H-SiC junction diodes have been investigated in the temperature range Т = 300 – 773 К. Analysis of the forward current-voltage characteristics and reverse current recovery waveforms shows that the lifetimeτ of non-equilibrium carriers in the base of the diodes steadily increases with temperature across the entire temperature interval. The rise in τ and decrease in carrier mobilities and diffusion coefficients with increasing temperature nearly compensate each other as regards their effect on the differential resistance of the diode, Rd. As a result, Rd is virtually temperature independent. An appreciable modulation of the base resistance takes place at room temperature even at a relatively small current density j of 20 A/cm2. At T = 800 K and j = 20 A/cm2, a very deep level of the base modulation has been observed. The bulk reverse current is governed by carrier generation in the space-charge region via a trap with activation energy of 1.62 eV. The surface leakage current of packaged structures does not exceed 2×10-6 А at T = 773 K and a reverse bias of 300 V.

Continuous-conduction-mode SEPIC converter with low reverse-recovery loss for power factor correction

A continuous-conduction-mode SEPIC converter with low reverse-recovery loss is proposed for power factor correction. The proposed SEPIC converter can reduce the reverse-recovery loss of the diodes and improve the power efficiency. By utilising a coupled inductor and an additional diode, zero-current turn-off of the output diode is achieved. The reverse-recovery current of the additional diode is reduced by the leakage inductor of the coupled inductor. The proposed SEPIC converter provides high power efficiency and high power factor compared to the conventional PFC circuits employing the SEPIC converter. An operation principle and a detailed analysis of the proposed converter are presented. Experimental results are discussed for a 300 W (330 V/0.9 A) prototype under the universal input voltage (90–265 V). It is shown that the efficiency of the SEPIC converter can be significantly improved.

High-performance front-end rectifier system for telecommunication power supplies

A high-performance front-end rectifier system is proposed for telecommunication power supplies. The proposed system consists of a boost converter for power-factor correction (PFC) and a asymmetrical half-bridge zeta converter for DC–DC power conversion. A cost-effective implementation for a continuous-conduction-mode boost converter is proposed for a PFC circuit. With a simple passive approach, the proposed PFC circuit minimises switching losses by reducing the reverse-recovery current. The asymmetrical half-bridge zeta converter operates under zero-voltage switching for the power switches and its output diode commutates with zero-current switching. The proposed front-end rectifier system is analysed and its design considerations are discussed. Experimental results for a 300 W prototype at a constant switching frequency of 100 kHz are presented to verify the analysis and to show the performance of the proposed system.

High Step-Up Converter With Coupled-Inductor

In this study, a high step-up converter with a coupled-inductor is investigated. In the proposed strategy, a coupled inductor with a lower-voltage-rated switch is used for raising the voltage gain (whether the switch is turned on or turned off). Moreover, a passive regenerative snubber is utilized for absorbing the energy of stray inductance so that the switch duty cycle can be operated under a wide range, and the related voltage gain is higher than other coupled-inductor-based converters. In addition, all devices in this scheme also have voltage-clamped properties and their voltage stresses are relatively smaller than the output voltage. Thus, it can select low-voltage low-conduction-loss devices, and there are no reverse-recovery currents within the diodes in this circuit. Furthermore, the closed-loop control methodology is utilized in the proposed scheme to overcome the voltage drift problem of the power source under the load variations. As a result, the proposed converter topology can promote the voltage gain of a conventional boost converter with a single inductor, and deal with the problem of the leakage inductor and demagnetization of transformer for a coupled-inductor-based converter. Some experimental results via examples of a proton exchange membrane fuel cell (PEMFC) power source and a traditional battery are given to demonstrate the effectiveness of the proposed power conversion strategy.

High-temperature (up to 773 K) operation of 6-kV 4H-SiC junction diodes

Steady-state and transient characteristics of packaged 6-kV 4H-SiC junction diodes have been investigated in the temperature range T = 300–773 K. Analysis of the forward current–voltage characteristics and reverse current recovery waveforms shows that the lifetime τ of non-equilibrium carriers steadily increases with temperature across the entire temperature interval. The rise in τ and decrease in carrier mobilities and diffusion coefficients with increasing temperature nearly compensate each other as regards their effect on the differential resistance of the diode, R d. As a result, R d is virtually temperature independent. The bulk reverse current is governed by carrier generation in the space-charge region via a trap with activation energy of 1.62 eV. The surface leakage current of packaged structures does not exceed 2 × 10 −6 A at T = 773 K and a reverse bias of 300 V.

Steady-State and Transient Characteristics of High-Voltage 4H-SiC Junction Diodes

Forward current-voltage characteristics, reverse current recovery and post-injection voltage decay are measured for high voltage 4H-SiC p+non+-diodes. The effects of both minority carrier lifetime in diode no-base and injection coefficient of p+-emitter are investigated with respect to device performance at high injection levels.

High-efficiency DC∕DC converter with high voltage gain

A high-efficiency converter with high voltage gain applied to a step-up power conversion is presented. In the proposed strategy, a high magnetising current charges the primary winding of the coupled inductor, and the clamped capacitor is discharged to the auxiliary capacitor when the switch is turned on. In contrast, the magnetising current flows continuously to boost the voltage in the secondary winding of the coupled inductor, and the voltages across the secondary winding of the coupled inductor, the clamped capacitor and the auxiliary capacitor are connected in series to charge the output circuit. Thus, the related voltage gain is higher than in conventional converter circuits. Moreover, this scheme has soft-switching and voltage-clamped properties, i.e. the switch is turned on under zero-current switching and its sustainable voltage is comparatively lower than the output voltage, so that it can select low-voltage low-conduction-loss devices and there are no reverse-recovery currents within the diodes in this circuit. In addition, closed-loop control methodology is utilised in the proposed scheme to overcome the voltage drift problem of the power source under the load variations. As a result, the proposed converter topology can promote the voltage gain for a conventional boost converter with a single inductor, and deal with the problem of the leakage inductor and demagnetisation of the transformer for a coupled-inductor-based converter. Some experimental results via examples of a proton exchange membrane fuel cell power source and a traditional battery are given to demonstrate the effectiveness of the proposed power conversion strategy.

A novel type of ultra fast and ultra soft recovery SiGe/Si heterojunction power diode with an ideal ohmic contact

A novel type of p+(SiGe)–n−–n+ heterojunction switching power diode with high-speed capability is presented to overcome the drawbacks of existing power diodes. The improvement is achieved by using a p+–n+ mosaic layer as a substitute for the n+ region in the conventional p+(SiGe)–n−–n+ diode to realize an `ideal ohmic' contact for electrons and holes simultaneously. Compared with conventional p+(SiGe)–n−–n+ diodes, the ideal ohmic contact p+(SiGe)–n−–n+ diodes have about one third of the reverse recovery time and a half of peak reverse recovery current. Furthermore, the softness factor increases nearly two times and the leakage current decreases 1–2 orders of magnitude. These improvements are achieved without resorting special process step to lower the carrier lifetime and thus the devices could be easily integrated into power ICs. The Ge percentage content of p+(SiGe) layer is an important parameter for the optimal device design.

Reverse Current Recovery in 4H-SiC Diodes with n- and p-Base

Reverse Current Recovery in 4H-SiC Diodes with n- and p-Base

Large area, ultra-high voltage 4H-SiC p-i-n rectifiers

This paper reports the design, fabrication and high temperature characteristics of 1 mm/sup 2/, 4 mm/sup 2/ and 9 mm/sup 2/ 4H-SiC p-i-n rectifiers with 6 kV, 5 kV, and 10 kV blocking voltage, respectively. These results were obtained from two lots in an effort to increase the total power levels on such rectifiers. An innovative design utilizing a highly doped p-type epitaxial anode layer and junction termination extension (JTE) were used in order to realize good on-state as well as stable blocking characteristics. For the 1 mm/sup 2/ and 4 mm/sup 2/ rectifier, a forward voltage drop of less than 5 V was observed at 500 A/cm/sup 2/ and the peak reverse recovery current shows a modest 50% increase in the 25/spl deg/C to 225/spl deg/C temperature range. On the 10 kV, 9 mm/sup 2/ rectifier, a forward voltage drop of less than 4.8 V was observed at 100 A/cm/sup 2/ in the entire 25/spl deg/C to 200/spl deg/C temperature range. For this device, the reverse recovery characteristics show a modest 110% increase in the peak reverse recovery current from 25/spl deg/C to 200/spl deg/C. A dramatically low Q/sub rr/ of 3.8 /spl mu/C was obtained at a forward current density of 220 A/cm/sup 2/ at 200/spl deg/C for this ultra high voltage rectifier. These devices show that more than three orders of magnitude reduction in reverse recovery charge is obtained in 4H-SiC rectifiers as compared to comparable Si rectifiers.